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Chapter 3
Description
General Information
The RUSKA Gas Lubricated Piston Pressure Gauge, model 2470 is a pneumatic pressure
standard designed for the accurate generation and measurement of gas pressures to
3000 psig. This measurement is accomplished in the basic manner of using the
fundamental pressure equation PRESSURE = FORCE/AREA (see Chapter 2, General
Piston Pressure Gauge Considerations, for more information). The gauge is used as the
precision measuring device in the RUSKA Gas Lubricated Piston Pressure Gauge System.
It may be seen from the above general equation that when a known force produced by a
known mass is applied to a piston of a known area, a pressure will be produced that may
be calculated (see Appendix A for detailed information). The RUSKA gauge is arranged
for the application of carefully determined masses on a piston of known area.
A key feature of the gauge is its ability to accurately reproduce its performance at the
lower pressures. The low viscosity of the gas provides excellent lubrication for the
close-fitting piston/cylinder assembly. Relative motion between the piston and cylinder is
necessary and is obtained by hand rotation of the masses and table which will then
distribute the gas molecules throughout the annulus of the assembly. It is the relative
absence of friction between piston and cylinder walls that characterizes the performance
for which the gauge is so highly respected.
The nominal range of pressure (interval) over which the gauge is capable of operating is
the span from 1.4 kPa (0.2 psig) to 20.6 MPa (3000 psig). This interval is covered by
three interchangeable piston/cylinder assemblies having sufficient overlap for
establishing continuity of measurement and for making detailed investigations of
subintervals within the total range (span).
Some of the most important industrial uses of the gas lubricated piston pressure gauge is
that of a standard for calibrating transducers, Bourdon-tube type gauges, manometers,
and other dead weight gauges. Frequently, the gauge is used in combination with the
pressure null transducer (RUSKA model 2413 or similar) for cross float calibrations
between gaseous and hydraulic media.